Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$206.82	8.401%	$224.1949	$224.19	$224.20	$224.20
Purchase #2	$182.94	8.321%	$198.1624	$198.16	$198.15	$198.20
Purchase #3	$37.25	10.786%	$41.2678	$41.27	$41.25	$41.30
Purchase #4	$148.61	5.282%	$156.4596	$156.46	$156.45	$156.50
Purchase #5	$171.51	10.514%	$189.5426	$189.54	$189.55	$189.50
Purchase #6	$217.30	12.648%	$244.7841	$244.78	$244.80	$244.80
Purchase #7	$159.63	7.392%	$171.4298	$171.43	$171.45	$171.40
7 purchase totals =	$1,124.06		$1,225.8412	$1,225.83	$1,225.85	$1,225.90